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CVE-2026-28496— FOSSBilling: Server-side template injection in Twig template rendering enables information disclosure and RCE

Quick assessment

Affected
FOSSBilling FOSSBilling
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

fossbilling是fossbilling团队开源的一种高效计费和客户管理方案。 FOSSBilling 0.8.0之前版本存在代码注入漏洞，该漏洞源于模板渲染系统存在服务器端模板注入漏洞，可能导致管理员注入任意Twig表达式，导致信息泄露和远程代码执行。

AI Predicted 9.1 Difficulty: Easy EPSS 1.91% · P79

Public Exploits 1

Nuclei · 1 CVE-2026-28496.yaml [template]

Affected Version Matrix 1

VendorProduct Version RangeStatus
FOSSBilling FOSSBilling < 0.8.0 affected
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I. Basic Information for CVE-2026-28496

Vulnerability Information
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Vulnerability Title
FOSSBilling: Server-side template injection in Twig template rendering enables information disclosure and RCE
Source: CVE Program / CVE List V5
Vulnerability Description
FOSSBilling is a free, open-source billing and client management system. Versions prior to 0.8.0 have a Server-Side Template Injection (SSTI) vulnerability in the template rendering system. Administrators with access to features that render Twig templates (email templates, mass mail campaigns, custom payment adapters, and the `string_render` API endpoint) can inject arbitrary Twig expressions, leading to information disclosure and remote code execution. The vulnerability exists because Twig templates are rendered without a sandbox, allowing access to the full Twig environment, API context, and the application's dependency injection container. Version 0.8.0 patches the issue. Some workarounds are available. Audit existing email templates for suspicious Twig expressions, rotate all admin and client API tokens, and/or block external access to /api/system/* at reverse proxy/WAF to mitigate chaining with GHSA-78x5-c8gw-8279.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1336
Source: CVE Program / CVE List V5
Vulnerability Title
fossbilling 代码注入漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
fossbilling是fossbilling团队开源的一种高效计费和客户管理方案。 FOSSBilling 0.8.0之前版本存在代码注入漏洞，该漏洞源于模板渲染系统存在服务器端模板注入漏洞，可能导致管理员注入任意Twig表达式，导致信息泄露和远程代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
FOSSBilling FOSSBilling < 0.8.0 -

II. Public POCs for CVE-2026-28496

# POC Description Source Link Shenlong Link
1 A Server-Side Template Injection (SSTI) vulnerability exists in FOSSBilling's template rendering system. Administrators with access to features that render Twig templates (email templates, mass mail campaigns, custom payment adapters, and the string_render API endpoint) can inject arbitrary Twig expressions, leading to information disclosure and remote code execution. The vulnerability exists because Twig templates are rendered without a sandbox, allowing access to the full Twig environment, API context, and the application's dependency injection container. https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-28496.yaml POC Details
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III. Intelligence Information for CVE-2026-28496

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Vendor Advisories for CVE-2026-28496 (2)

Same Patch Batch · FOSSBilling · 2026-06-23 · 4 CVEs total

CVE-2026-27604 FOSSBilling: Improper API Role Validation (system) Enables Unauthenticated Access to Privi
CVE-2026-23513 FOSSBilling: Broken Authorization in Client Transaction and Order Listings
CVE-2025-64105 FOSSBilling: IDOR Vulnerability in Support Ticket Creation

IV. Related Vulnerabilities

Same product: FOSSBilling
Same vendor: FOSSBilling
Same weakness: CWE-1336

V. Comments for CVE-2026-28496

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